Things to Know About Zika Virus

The Centers for Disease Control and Prevention has warned pregnant women to avoid travel to at least 24 countries and territories where Zika virus is circulating, including Brazil, Mexico, Puerto Rico and the U.S. Virgin Islands. The virus usually causes only mild disease, but it has been linked to a serious birth defect in the infants of women who are infected during their pregnancies as well as a rare neurological disorder in adults. Here are a few things to know about Zika.

Zika is a tropical disease, like yellow fever and dengue. It is spread to people through mosquito bites, not person to person. About one in five people who are infected with Zika virus will develop symptoms, the most common of which are fever, rash, joint pain and conjunctivitis, or redness in the eyes. Other symptoms are muscle pain and headache. Symptoms usually begin two to seven days after infection through a mosquito bite. It’s usually a mild disease lasting a few days or a week, and rarely requires hospitalization.

The virus was first identified in Uganda in 1947, and has caused outbreaks in Africa, Southeast Asia and on several Pacific Islands. It is believed to have crossed the Pacific and been introduced into Brazil in 2014, where its largest outbreak ever has occurred. Zika has been spreading rapidly through the Western hemisphere since then.

Zika poses a significant risk for pregnant women. There is strong evidence of a link between the Zika virus and a birth defect called microcephaly in which babies are born with undersized brains and skulls, according to the Centers for Disease Control and Prevention. Brazil’s health ministry has reported several thousand cases of suspected Zika-related microcephaly since October 2015.

The CDC has warned pregnant women to avoid travel to 24 countries and territories, mostly in Central and South America and the Caribbean. It has also urged women who are trying to become pregnant to talk with their doctors about the planned trip, and to protect themselves from mosquitoes if they do go.

Pregnant women are likely most at risk during their first trimester, when brain development is occurring, the CDC says, but adds there is evidence the risk continues into the second trimester as well.

Pregnant women who have already traveled to a country where Zika is circulating should be evaluated by their doctors for infection, the CDC says. It’s possible that the baby may be affected even if the mother doesn’t develop symptoms herself. Women who test positive for Zika should be given regular ultrasounds to monitor the development of their babies, the CDC says.

Also of concern to international health authorities is a suspected link between Zika and an increase in the number of cases of Guillain-Barre syndrome, a rare disorder in which the body’s immune system attacks nerve cells. It can cause temporary paralysis that can last for weeks. The CDC is investigating the possible link between Zika and Guillain-Barre syndrome.

The CDC has warned pregnant women to avoid travel to 24 countries and territories, mostly in Central and South America and the Caribbean.

Scientists believe that infected pregnant women pass the virus to their unborn babies through the placenta, and that the virus then damages their brain development. Tests in CDC labs found the virus in the placentas of two fetuses that had had microcephaly and miscarried, and in the brains of two full-term babies who were born with microcephaly and died. But the tests didn’t show how the virus causes the birth defects. More studies are under way or planned to find that out, researchers say.

Researchers are also studying the rise in cases of microcephaly in Brazil to try to determine how many of them are due to Zika rather than other factors.

Zika is spread primarily by the Aedes aegypti mosquito, commonly known as the yellow fever mosquito. In the U.S., its range runs from South Carolina and Florida along the Gulf Coast to Texas, as well as Hawaii and some parts of Arizona. Zika is also spread, perhaps to a lesser extent, by Aedes albopictus, also known as the Asian tiger mosquito, whose range in the summer can reach as far north as New York and New Jersey, as well as parts of Illinois and Indiana.

The CDC says that outbreaks of dengue and chikungunya, viruses which are spread by the same mosquitoes, have been very limited in the U.S., suggesting that Zika outbreaks in the continental U.S. would likely follow the same pattern. Air conditioning, good sanitation, window and door screens–all more common in the U.S. than in countries already hit by the virus–all help cut down on transmission. Mosquito control programs across the U.S. conduct regular surveillance for such viruses, and spray to reduce transmission. Health authorities are increasing surveillance for Zika in the U.S.

There is no vaccine for Zika. Do everything you can to protect yourself from mosquito bites. Aedes mosquitoes are very aggressive and bite during the day, often around the ankles and knees. Wear mosquito repellent containing DEET or other ingredients that provide long lasting protection. Wear long-sleeved clothing when you can.

Aedes aegypti breed in small pools of water, often those in front yards and backyards of homes: flower pots, tires, even tiny pockets of water in childrens’ toys. Remove as many of these containers as you can from the area around your home.

This copy is for your personal, non-commercial use only. Distribution and use of this material are governed by our Subscriber Agreement and by copyright law. For non-personal use or to order multiple copies, please contact Dow Jones Reprints at 1-800-843-0008 or visit www.djreprints.com.